4.88 rear end

[Weaver7]

I have a 1980 RX7 with a 4.88 "welded" rear differential. My question is the car seems to make quite a bit of noise from the rear when driving slow is this normal?? Also if you shake the rear end of the car side to side I can hear a clunking. Thanks in advance for any help you can give me.

[ScottNutter]

I can't say what your clunking is but mine was caused by one of the collars comming loose, I needed to press it back on. Thought maybe it was cause I'm such a fast driver Then after realizing that I am just not that fast, started looking for other reasons why it came loose and found that the rotor was .021" out as opposed to .004" maximum. So I would suggest pulling your axles and checking the free play in the bearings. As for noise I am not sure but I know that my LSD chatters.

[Quickshoe]

Originally posted by Weaver7:
Also if you shake the rear end of the car side to side I can hear a clunking. Thanks in advance for any help you can give me.

I have had this same problem with 2 prior rx7's. My clunking noise was coming from the heim end on the RH side of the panhard bar. The jamb nut would come loose about every 5hrs of track time. I checked it OFTEN.

[TURN9]

I don't know if this is any help to you, but out west some of us have welded 3.90s and they are a pain to push if you ever have to. the axle collar bearings would come loose at tomes and we would take a piece of pipe and slip it over the axle, and proceed to "slide hammer" the bearing until the outer ring wouldn't spin by hand.

The weld should be on both sets of spider gears. one can't weld enough, too little will break loose.

I ran in PRO-7 with a welded, and liked the consistancy of it being locked. Never tried a limited though. I know in conering I've been told a limited is far better, but a welded in breaking is far better. Any takers?

Corey.

[TURN9]

That was a non-limited slip welded rear, and it never made any noise.

Corey.

[CrunchyFrog]

Oftentimes you will find that the drive shaft takes a beating from a welded diff - not sure why but they do crap out...

As far as any particular wear on the Rx7 diff's - I have no idea and I can't comment.

As far as a welded 1st Gen.Rx7 diff, they are know to cause understeer - not a problem until you are trying to catch an equally well driven LSD equiped car, then you will notice corner entry to be slower due to the extra push.

K

[Weaver7]

Originally posted by TURN9:
That was a non-limited slip welded rear, and it never made any noise.

Corey.

Do you reccomend a LSD vs. the welded rear and if so where can I pick one up at a reasonable price???

[CrunchyFrog]

You should be able to get your current one fitted with an LSD - or your LSD repaired at a reasonable cost.

[Mike Cox]

Having run both a welded 4.88 and a limited slip 4.88, I know prefer the LSD. 2.5 seconds quicker on the same course configuration made up my mind. Yes I said 2.5 seconds faster. At Sebring , on the club course, there are 2 corners that you are not going fast enough to break the rear end loose
and my car didn't push in those 2 corners, it bound up and wouldn't accelerate until I unrolled the steering wheel. Now with the LSD my car flies thru the corners and my shift points backed up almost 200 feet. Must mean I'm going faster. So, for all practical situations, I will not go back to the welded setup as the LSD has freed my car up and I'm challenging for the win instead of settling for 3rd place.

[TURN9]

I would have to agree with the facts of times versus welded consistancy. Most junk yards have complete rear axle assy's for 1st gens and the like. I would recommend using a good synthetic oil for the rear end.

I was under the impression that a limited locks in straight line and slips and unslips in cornering. Can anyone verify this?

Corey.

[CrunchyFrog]

Easy answer is imagine that there are these little clutch plates all pressed tightly against each other, they are moving together in the same direction when moving in a straight line, but as the car turns the outside wheel is moving in a larger circle to the inner wheel this starts the clutches sliding past each other.

This is the Limited bit...

if it were my car the first thing i would suspect is one or both of the outer axel bearings has play and need changed, take the wheels off and the calipers and push and pull on the flanges too see if they is any play.

------------------
Daryl Brightwell
ITA Mazda #77
SFR, NORPAC
CSCC, SOPAC

[Quickshoe]

Weaver7,

Some have posted some likely causes, all require some degree of teardown. If you have a panhard bar, I would again suggest you check the heim ends. It's the simplest cause to eliminate...Maybe the welded nuts (not bungs) simply don't provide enough grip area for the heim end and something was going on, because my jamb nuts were tight (too tight?) Of course maybe it was just me and I was simply pulling too many g's thru the corners for a bar engineered for mere wankers

[Weaver7]

Originally posted by Quickshoe:
Weaver7,

Some have posted some likely causes, all require some degree of teardown. If you have a panhard bar, I would again suggest you check the heim ends. It's the simplest cause to eliminate...Maybe the welded nuts (not bungs) simply don't provide enough grip area for the heim end and something was going on, because my jamb nuts were tight (too tight?) Of course maybe it was just me and I was simply pulling too many g's thru the corners for a bar engineered for mere wankers

Thank you everyone for all of your help. I'm seriously going to consider getting a LSD for my car. Thanks again.

[Allen Brown]

I run a 85 SE where I have added MazdaComps oversized clutch plates. Definately tighter than the stock LSD, but still allows the rear tires to turn at different speeds. Very happy with the setup.

[CrunchyFrog]

Nice - thanks Allen - this is good news.